In general, hydraulic brakes operate for braking by pressing pads against a disc using hydraulic pressure. The hydraulic brakes have complicated configurations and some limits in improving reliability of braking performance and safety. On the other hands, electromechanical brakes (EMB) have rather simple configurations and good reliability of braking performance. Thus, EMB have been increasingly used. The EMB achieves braking by directly converting the power of a motor into a straight moving force.
As an EMB using power of a motor, an EWB (Electro Wedge Brake) has been proposed, which achieves braking, using a wedge action that boosts an input force by pressing brake pads against a disc to create friction by using a wedge assembly that is operated by an actuator for braking. The EMB and EWB are generally called a BBW (Brake By Wire) technology.
However, the electromechanical brake should be operated at 12V and achieves braking using electronic signals and electric devices, such that it has a basic limit in that FR (Failure Rate) increases as compared with the hydraulic brake system.
Therefore, various methods have been developed to reduce the FR (Failure Rate) to the same level as the stable hydraulic brake system. For example, the FR (Failure Rate) is reduced by achieving F-S (Fail-Safe) by configuring a control logic that controls the EWB or EMB and a circuit reflecting it; however, this method is not provided with a device that mechanically generates a braking force when a motor, which is a power source, fails. Accordingly, the safety is deteriorated and the method gives a cause that makes it difficult to practically apply to vehicles due to the reduction of safety.